Decay kinetics of excess electrons in crystalline ice

Journal Article · Thu May 15 04:00:00 EDT 1980 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100447a035· OSTI ID:5154486

Warman, J M ^[1]; de Haas, M P; Verberne, J B

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1. Interuniversity Reactor Inst., Delft, Netherlands

The decay kinetics of highly mobile excess electrons formed on nanosecond pulse radiolysis of crystalline ice have been studied from -10 to -190/sup 0/C by using the microwave absorption method. The overall decay is controlled by four processes, two of which involve preexisting trapping sites present in the lattice and two others which involve reaction with products of irradiation formed in the pulse. The lattice trapping sites are tentatively assigned to a vacancy combined with a Bjerrum D defect (dressed vacancy) and a normal lattice vacancy. The former results in an electron decay rate (rate constant x trap concentration) of 1.1 x 10/sup 19/ exp(-0.48/kT) s/sup -1/, for kT in eV, above -80/sup 0/C and less than or equal to 10/sup 6/ s/sup -1/ below -100/sup 0/C. The latter is operative below -140/sup 0/C and presents a shallow trap, ..delta..H = -0.1 to -0.2 eV, for electrons. The main radiation product responsible for electron decay is the positive counterion. The electron-ion recombination rate constant is given by the Debye expression with a temperature-independent value of the effective dielectric constant epsilon/sub r/ of 2.1 +- 0.2. Based on an infinitely short pulse the first half-life of mobile electrons toward recombination is approximately 500/R ns over the temperature range -120 to -50/sup 0/C, where R is the dose in the pulse in rads. The second product of irradiation which is thought to react with electrons is the OH radical with a rate constant of 3 x 10/sup 14//G(OH) dm/sup 3/ mol/sup -1/ (100 eV). The product of the electron mobility and the free-ion yield is found to increase from 3.0 x 10/sup -4/ to 4.2 x 10/sup -4/ m/sup 2/ V/sup -1/ s/sup -1/ (100 eV)-/sup 1/ over the temperature range -120 to -50/sup 0/C. Evidence for a second mobile species, thought to be the hole, with a mobility of ca. 1 x 10/sup -6/ m/sup 2/ V/sup -1/ s/sup -1/ and a lifetime of 50 to 100 ns is found above -40/sup 0/C.

• OSTI ID: 5154486
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 84:10; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400600* -- Radiation Chemistry
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
DATA
DATA FORMS
DECOMPOSITION
ELECTRON MOBILITY
ELECTRONS
ELEMENTARY PARTICLES
EXPERIMENTAL DATA
FERMIONS
ICE
INFORMATION
ISOLATED VALUES
KINETICS
LEPTONS
MOBILITY
NUMERICAL DATA
PARTICLE MOBILITY
RADIATION CHEMISTRY
RADIATION EFFECTS
RADIOLYSIS
REACTION KINETICS